Anyone else have to follow a diet due to health conditions? How do you do it?

I have genetic PCOS and chronic gastritis and I have been struggling to adhere to a diet for years. I’m sick of feeling shitty every day and knowing it’s because I’m not eating right. I have a hard time forcing myself to eat foods that don’t sound good, I usually would rather just forgo the meal. Or I cave and end up eating what I want anyway for the dopamine. Ideally, I need to be on a low carb/sugar, high protein/fiber diet. Due to the gastritis, I also have a super sensitive stomach and can’t tolerate anything irritating without either pain, intense heartburn, or bloating (think caffeine, alcohol, fried/fatty food, spicy, acidity, dairy).

I’m struggling to figure out what to purchase at the grocery store. I’m completely lost on hitting nutritional goals. Another huge factor is that I’m in-between jobs and have an incredibly low budget right now. If anyone is in a similar situation or has any advice, I would appreciate it!